Anyone out there who's gone from a 285/70/17 to a 315/70/17 notice a drop in power?
OR you can load the 120 tune and get more bottom, mid and topIt is because you are gearing the truck higher by putting bigger tires on it. A larger tire travels further for every revolution. That is exactly what a transmission does. Each gear changes how far in distance the truck travels for every revolution of the driveshaft or crank shaft.
It takes more power or torque to move a vehicle with larger tires because you are asking it to move further for every revoulution. It is like taking 3.73's out and putting a 3.08 in there and keeping the stock tires. If you keep your big tires and put 4.10s in it, then you will get the bottom end back in it.